Sources
otldr computes what it can and cites the rest. These are the primary references and libraries behind the data on this site. Individual reference pages also list the specific sources used for that page. See methodology for how they are applied.
Computation libraries
The engines we use to compute positions, phases and retrogrades.
- astronomy-engine
VSOP87 + ELP-2000; planetary positions, Moon phases, retrograde stations, ingresses.
- Swiss Ephemeris (Astrodienst)
Reference ephemeris used for asteroid positions (Ceres, Pallas, Juno, Vesta, Chiron).
Astronomical authorities
Primary references for physical facts about the Solar System and sky.
- NASA — Solar System & Moon
Orbital periods, Moon phases, asteroid and dwarf-planet data.
- International Astronomical Union (IAU)
Constellation boundaries; the 2006 planet / dwarf-planet definitions.
- U.S. Naval Observatory — Astronomical Applications
Independent reference for Moon-phase dates and times.
Reference & tradition
Encyclopaedic and traditional references for definitions and astrological conventions.
- Encyclopaedia Britannica
Zodiac, horoscope, precession and general background.
- Astrodienst Astrowiki (astro.com)
Astrological terminology and chart conventions, labelled as tradition.